Harutaka HATA*1 and Hiroyuki MOTOMURA2
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ACTA ICHTHYOLOGICA ET PISCATORIA (2020) 50 (3): 367–372 DOI: 10.3750/AIEP/03015 FIRST NORTHERN HEMISPHERE RECORDS OF THE SAMOAN ANCHOVY, STOLEPHORUS APIENSIS (ACTINOPTERYGII: CLUPEIFORMES: ENGRAULIDAE) Harutaka HATA *1 and Hiroyuki MOTOMURA 2 1 Center for Molecular Biodiversity Research, National Museum of Nature and Science, Amakubo, Tsukuba, Ibaraki, Japan 2 The Kagoshima University Museum, Kagoshima, Japan Hata H., Motomura H. 2020. First Northern Hemisphere records of the Samoan anchovy, Stolephorus apiensis (Actinopterygii: Clupeiformes: Engraulidae). Acta Ichthyol. Piscat. 50 (3): 367–372. Abstract. Two Japanese specimens of the Samoan anchovy, Stolephorus apiensis (Jordan et Seale, 1906), previously known only from Papua New Guinea, Fiji, and Samoa, were confirmed during a revisionary taxonomic study of the genus. Although S. apiensis has been redescribed recently, details of its distributional range and habitat have remained unclear. The presently reported study sought to clarify some aspects of both. Two specimens of S. apiensis were examined, counts and proportional measurements following Hata and Motomura (2017). All measurements were made with digital calipers to the nearest 0.01 mm. Institutional codes follow Sabaj (2019). Two specimens, collected from Japanese river estuaries, represent the first Northern Hemisphere records of S. apiensis, extending the northern limit of the species’ distribution by approx. 4300 km. Stolephorus apiensis is considered to be widely distributed in the western Pacific from southern Japan to Samoa, most likely as a sometime inhabitant of estuarine waters. The new standard Japanese name “Nampu-ainokoiwashi” is proposed for the species. Keywords: Stolephorus commersonnii, Stolephorus insignus, Shikoku, Ryukyu Islands, Japan INTRODUCTION Kochi Prefecture and Urauchi River estuary, Iriomote- Stolephorus Lacepède, 1803, an Indo-Pacific genus jima Island, Japan, were found in the collections of the of marine and/or brackish water anchovies (Engraulidae), Faculty of Science, Department of Natural Science, comprises 26 valid species (Whitehead et al. 1988, Kochi University and Okinawa Churashima Foundation, Wongratana et al. 1999, Kimura et al. 2009, Hata and respectively. They were identified asStolephorus apiensis Motomura 2018a, 2018b, Hata et al. 2019, 2020, Gangan et (Jordan et Seale, 1906), previously recorded only from al. 2020), many being abundantly caught and marketed in New Ireland (Papua New Guinea), Fiji, and Samoa (Hata tropical Asia (Rau and Rau 1980, Talwar and Kacker 1984, and Motomura 2018b, Fricke et al. 2019). The present Conlu 1986, Phui Kong 1998, White et al. 2013, Psomadakis specimens, described in detail herein, represent the first et al. 2015, 2019, Hata 2018b, 2019, Hata et al. 2020), Japanese records of the species, the Kochi specimen also although rarely seen off Japan. In fact, only two species, being the northernmost record known. Stolephorus commersonnii Lacepède, 1803 and Stolephorus indicus (van Hasselt, 1823), have been formally recorded MATERIALS AND METHODS from Japanese waters (Nishishimamoto 1963a, Kimura et al. Counts and proportional measurements, expressed as 1999, Aonuma and Yagishita, 2013b). The occurrence and percentages of standard length (SL), followed Hata and catch of S. indicus off southern Japan, including Kyushu Motomura (2017). All measurements were made with and the Ryukyu Islands, are comparatively rare (Miura digital calipers to the nearest 0.01 mm. Institutional codes 2012, Hata 2017, 2018a, Kobayashi 2019), and records of follow Sabaj (2019). S. commersonnii from Japanese waters even more limited [so deficient in habitat and biological information (Kimura et al. RESULTS 1999, Yoshigou 2014) that the species is ranked as “DD (Data Family ENGRAULIDAE Deficient)” in the Red List of threatened marine fishes issued Stolephorus apiensis (Jordan et Seale, 1906) by the Ministry of the Environment, Government of Japan]. [English name: Samoan Anchovy; new standard Japanese During a revisionary study of the genus, two engraulid name: Nampu-ainokoiwashi] specimens collected from the Shimanto River estuary, (Fig. 1; Tables 1, 2) * Correspondence: Dr. Harutaka Hata, 茨城県つくば市天久保4-1-1 国立科学博物館分子生物多様性研究資料センター，phone: +81 080-1327-1935, e-mail: (HH) [email protected], (HM) [email protected]. 368 Hata and Motomura Material examined. 2 specimens, 53.0–54.2 mm fin origin. Posterior tip of depressed pelvic fin reaching to SL. BSKU 55110, 54.2 mm SL, approx. 400 m below the vertical through third or fifth dorsal-fin ray base. Caudal junction of the Takeshima and Nabeshima rivers (Shimanto fin forked, tips of both lobes pointed. Basin), Shimanto City, Kochi Prefecture, southern Japan, Coloration of preserved specimens. Body uniformly 12 October 1999; URM-P 15468, 53.0 mm SL, estuary pale ivory. Indistinct light brown longitudinal band of Urauchi River, Iriomote-jima Island, Ryukyu Islands, narrower than eye running from opercle to caudal-fin Japan, 18 August 1985. base. Paired dark patches on parietal and occipital regions Description. Counts and measurements, expressed as (those on occipital region relatively indistinct; Fig. 2B, E). percentages of SL or HL, given in Tables 1 and 2. Body No dark lines on dorsum. Melanophores scattered along laterally compressed, elongate, deepest at dorsal fin origin. scale pockets on dorsum, a few on snout tip, no black spots Dorsal profile of head and body gently elevated from below eye and lower-jaw tip. Fins pale, semi-transparent. snout tip to dorsal fin origin, thereafter gradually lowering Melanophores scattered along caudal-fin rays. to uppermost point of caudal fin base. Ventral profile of Distribution. Stolephorus apiensis has been previously head and body gently lowering from lower-jaw tip to recorded from Papua New Guinea (New Ireland), Fiji, and below pectoral fin, thereafter nearly straight (parallel to Samoa (Whitehead et al. 1988, Wongratana et al. 1999, body axis) to anal fin origin, gradually elevated along anal Hata and Motomura 2018b, Fricke et al. 2019), and is here fin base, thereafter nearly straight (parallel to body axis) newly recorded from Japan (Yaeyama Islands and Kochi to lowermost point of caudal fin base. Abdomen rounded, Prefecture). covered with three or five spine-like scutes anterior to pelvic fin insertion. Pelvic scute without spine. Postpelvic DISCUSSION and predorsal scutes absent. Anus just anterior to anal The specimens collected from Japan were assigned to fin origin. Snout round, projecting, length less than eye the genus Stolephorus, as defined by Whitehead et al. (1988) diameter. Eye large, round, covered with adipose eyelid, and Wongratana et al. (1999), due to having a long isthmus positioned laterally on head dorsal to horizontal through muscle reaching anteriorly to the posterior margin of the pectoral fin insertion, visible in dorsal view. Pupil round. gill membrane, and hidden urohyal and prepelvic scutes, Orbit elliptical. Nostrils close to each other, anterior to and the absence of postpelvic scutes. The specimens were orbit. Mouth large, inferior, ventral to body axis, extending further identified on the basis of the following combination backward beyond posterior margin of eye. Maxilla rather of characters, closely matching the diagnostic features of long, its posterior tip slightly short of posterior margin Stolephorus apiensis given by Whitehead et al. (1988), of preopercle. Lower jaw slender. Single row of conical Wongratana et al. (1999), and Hata and Motomura (2018b): teeth on each jaw and palatines. Several conical teeth on maxilla rather long, its posterior tip slightly short of vomer. Small fine teeth on pterygoids. Posterior margins posterior margin of preopercle; no predorsal scutes; pelvic of preopercle, subopercle and opercle rounded, smooth scute without spine; posterior margin of preopercle round, (opercle broken on both sides in BSKU 55110). Gill convex; paired obscure dark patches on parietal and occipital membrane without serrations. Interorbital space flat. regions without following dark lines; black spots below Interorbital width less than eye diameter. Pseudobranchial eye and lower-jaw tip absent; body elongate, posterior tip filaments present, length of longest filament less than eye of depressed pelvic fin reaching to vertical through third or diameter. Gill rakers long, slender, rough, visible from fifth dorsal-fin ray origin; gill rakers numerous, 21 + 27–28 side of head when mouth opened. Isthmus muscle long, = 48–50 (1st gill arch), 15 + 25–26 = 40–41 (2nd), 11–12 reaching anteriorly to posterior margin of gill membranes. + 15 = 26–27 (3rd), 10 + 12 = 22 (4th) on each gill arch; Urohyal hidden by isthmus muscle (not visible without body elongate, its depth 18.6%–19.4% of SL; anal fin base dissection). Gill membrane on each side joined distally, long, its length 20.2%–20.6% of SL; caudal peduncle short, most of isthmus muscle exposed (not covered by gill its length 17.5%–17.7% of SL. In addition, the meristics membrane). Head scales absent. Lateral line absent. Fins and morphometrics of the presently reported specimens scaleless, except for broad triangular sheath of scales on closely matched those of S. apiensis given by Hata and caudal fin. Dorsal fin origin posterior to vertical through Motomura (2018b) (Tables 1, 2). Only two Stolephorus base of last pelvic-fin ray, slightly posterior to middle of species, Stolephorus commersonnii Lacepède, 1803 and body. Dorsal and anal fins with three anteriormost rays Stolephorus indicus